Conventional bar codes have varying width bars and spaces suitably printed on a label. The bar code may take any conventional form in one or more dimensions, and includes, for example, the typical one-dimensional UPC form. The UPC symbology is based on a specification enacted by the Uniform Product Code Council, Inc. of Dayton Ohio. The typical UPC bar code includes a series or sequence of alternating dark bars and light spaces of varying widths. The bars and spaces are arranged in groups representing individual characters. The bar code starts with a left margin character and ends with a right margin character, and has a center reference character as well, with the characters provided there between representing any desired data.
The minimum width of either a bar or space in the UPC symbology is defined as a single module, which represents a unit width. The width of a single character coded using the UPC symbology is seven (7) modules. A seven module UPC character has two bar and two space elements which have varying widths to differentiate between the respective characters.
With the introduction of RSS bar code tags along side UPC tags into the market place, today's scanners must have higher density scan line patterns to be able to sustain high levels of performance. To consistently read the small RSS tags, the scanner must produce a scan pattern without any holes that would allow the tag to pass through without being read. The NCR 788X series single window bar code scanners have the highest density pattern available for this sized scanner, see FIG. 1a. However, its scan pattern is not dense enough for the small RSS tags.
Clearly there is a limit to the number and density of scan lines that can be produced by conventional scanners, without increasing the size of the scanner.
It is an object of the present invention to produce a bar code scanner, which obviates the problems discussed above.